Shall we talk about the extra bit of bass added to the prop to allow the cables to hang from the car elevated platform?

Someone is being nostalgic, it might be me.

It is it appears a couple of inches have been added to the base of the box to house the cables.

Interesting to see that book cover - someone's flight of fancy on the inner workings of the Tardis! Shame they got the roof stacks so wrong!
As for the extra piece on the base - it wouldn't surprise me if it's also there to protect the prop from the hoist/lift as much as providing somewhere to attach all those tubes.

Just my tuppence but I'd say the additional section on the base is to allow the fascia of the prop enough depth to support its weight on the hoist runners. The extra piece looks to be too shallow to hide all those cables and pipework.